Routines
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49400: Draw Town
Used by the routine at InitialiseGame.
Called every frame. In the town, it draws the walls and the objects of the cells which are around the sheriff, in an order which is chosen so that the cells nearer the viewer are drawn after the ones behind them. The order depends on which of five of the cells next to the sheriff's cell have buildings in them, and is taken from five-byte entries in a table at DrawingOrders. Each of the five bytes holds the offset of a cell from the sheriff's cell (bits 4 and 5 for the offset in the column, bits 6 and 7 for the offset in the row) and a kind of drawing to do in it (bits 0 and 1): 0 draws the objects in the cell, 1 draws the walls and 2 draws the edges. The sheriff's cell and three of its neighbours are drawn last. The town is a map of sixteen cells by sixteen, and when the view is rotated the cell numbers are turned round.
town
Return if this is not the town.
DrawTown 49400 LD A,(41575) Fetch TownOffset.
49403 AND A Return if it is not.
49404 RET Z
The walls are not drawn on columns of the screen which already have a wall in them. The sixteen flags at ColumnFlags cover columns of sixteen pixels. The left sixteen pixels and the right forty eight sit outside the play area, so they are marked as done.
49405 LD HL,57345 Set ColumnFlags.
49408 LD (41544),HL
Fetch the sheriff's cell.
49411 LD A,(41599) Fetch the horizontal cell of the sheriff from 41599 and keep it in L.
49414 LD L,A
49415 LD A,(41601) Fetch the vertical cell of the sheriff from 41601 and keep it in H.
49418 LD H,A
Turn the cell round if the view is rotated.
49419 CALL ConvertCell Call ConvertCell.
49422 PUSH HL Stash the cell of the sheriff on the stack.
49423 LD E,0 Clear the flags for the neighbouring cells.
Find out which of five neighbouring cells have something in them. Taking the column and row of the sheriff's cell as x and y, they are the cells (x-1, y+1), (x-1, y), (x, y+1), (x-1, y-1) and (x+1, y+1).
49425 DEC L Take one off the column...
49426 INC H ...and add one to the row.
Find the contents of the cell.
49427 CALL GetMapCell Call GetMapCell.
49430 JR Z,DrawTown_TestSecondCell Jump to DrawTown_TestSecondCell if it is empty.
49432 SET 0,E Set the bit for the first cell.
Test the cell at (x-1, y).
DrawTown_TestSecondCell 49434 POP HL Restore the cell of the sheriff from the stack.
49435 PUSH HL Stash the cell of the sheriff on the stack.
49436 DEC L Take one off the column.
Find the contents of the cell.
49437 CALL GetMapCell Call GetMapCell.
49440 JR Z,DrawTown_TestThirdCell Jump to DrawTown_TestThirdCell if it is empty.
49442 SET 1,E Set the bit for the second cell.
Test the cell at (x, y+1).
DrawTown_TestThirdCell 49444 POP HL Restore the cell of the sheriff from the stack.
49445 PUSH HL Stash the cell of the sheriff on the stack.
49446 INC H Add one to the row.
Find the contents of the cell.
49447 CALL GetMapCell Call GetMapCell.
49450 JR Z,DrawTown_TestFourthCell Jump to DrawTown_TestFourthCell if it is empty.
49452 SET 2,E Set the bit for the third cell.
Test the cell at (x-1, y-1).
DrawTown_TestFourthCell 49454 POP HL Restore the cell of the sheriff from the stack.
49455 PUSH HL Stash the cell of the sheriff on the stack.
49456 DEC L Take one off the column...
49457 DEC H ...and take one off the row.
Find the contents of the cell.
49458 CALL GetMapCell Call GetMapCell.
49461 JR Z,DrawTown_TestFifthCell Jump to DrawTown_TestFifthCell if it is empty.
49463 SET 3,E Set the bit for the fourth cell.
Test the cell at (x+1, y+1).
DrawTown_TestFifthCell 49465 POP HL Restore the cell of the sheriff from the stack.
49466 PUSH HL Stash the cell of the sheriff on the stack.
49467 INC L Add one to the column...
49468 INC H ...and add one to the row.
Find the contents of the cell.
49469 CALL GetMapCell Call GetMapCell.
49472 JR Z,DrawTown_FindEntry Jump to DrawTown_FindEntry if it is empty.
49474 SET 4,E Set the bit for the fifth cell.
Point at the entry in the table of five bytes for the cells which have been found.
DrawTown_FindEntry 49476 LD D,0 Clear D.
49478 LD A,E Fetch the flags for the cells.
49479 EX DE,HL Move the flags into HL.
49480 LD E,L Copy them into DE.
49481 LD D,H
49482 ADD HL,HL Multiply them by four.
49483 ADD HL,HL
49484 ADD HL,DE Add them again, to make five times.
49485 LD DE,24753 Point DE at DrawingOrders.
49488 ADD HL,DE Point HL at the entry.
49489 EX DE,HL Keep the address of the entry in DE.
49490 LD B,5 Set the number of bytes to five.
Draw the next cell from the entry.
DrawTown_NextCell 49492 POP HL Restore the cell of the sheriff from the stack.
49493 PUSH HL Stash the cell of the sheriff on the stack.
49494 LD A,(DE) Fetch the byte from the entry.
49495 INC DE Move on to the next byte.
49496 BIT 5,A Jump to DrawTown_TestRow if the cell is in the same column as the sheriff.
49498 JR NZ,DrawTown_TestRow
49500 BIT 4,A Jump to DrawTown_ColumnOffset if this is not the next column.
49502 JR Z,DrawTown_ColumnOffset
49504 INC L Add two to the column.
49505 INC L
DrawTown_ColumnOffset 49506 DEC L Take one off the column, to make it one lower or one higher.
DrawTown_TestRow 49507 BIT 7,A Jump to DrawTown_KeepKind if the cell is in the same row as the sheriff.
49509 JR NZ,DrawTown_KeepKind
49511 BIT 6,A Jump to DrawTown_RowOffset if this is not the next row.
49513 JR Z,DrawTown_RowOffset
49515 INC H Add two to the row.
49516 INC H
DrawTown_RowOffset 49517 DEC H Take one off the row, to make it one lower or one higher.
Choose what to draw in the cell.
DrawTown_KeepKind 49518 AND %00000011 Keep the kind of drawing.
49520 PUSH BC Stash the number of bytes left and the address in the entry on the stack.
49521 PUSH DE
Make the draw routine return to DrawTown_AfterDraw.
49522 LD DE,49538 Point DE at DrawTown_AfterDraw.
49525 PUSH DE Stash it on the stack.
Draw the objects in the cell if the kind is zero.
49526 JP Z,DrawCellObjects Jump to DrawCellObjects if it is.
49529 DEC A Take one off the kind.
Draw the walls of the cell if the kind is one.
49530 JP Z,DrawCellWithWalls Jump to DrawCellWithWalls if it is.
49533 DEC A Take one off the kind.
Draw the edges of the cell if the kind is two.
49534 JP Z,DrawCell Jump to DrawCell if it is.
The kind is three, which is nothing.
49537 POP DE Throw away the return address from the stack.
DrawTown_AfterDraw 49538 POP DE Restore the address in the entry and the number of bytes left from the stack.
49539 POP BC
Go back for the next byte of the entry.
49540 DJNZ DrawTown_NextCell Jump to DrawTown_NextCell if there are any left.
Draw the sheriff's cell and the three cells after it: the cells with the row one lower, the column one higher, and both of those.
49542 POP HL Restore the cell of the sheriff from the stack.
49543 PUSH HL Stash the cell of the sheriff on the stack.
Draw the edges and the objects in the cell.
49544 CALL DrawCellAndObjects Call DrawCellAndObjects.
49547 POP HL Restore the cell of the sheriff from the stack.
49548 PUSH HL Stash the cell of the sheriff on the stack.
49549 DEC H Take one off the row.
Draw the edges and the objects in the cell.
49550 CALL DrawCellAndObjects Call DrawCellAndObjects.
49553 POP HL Restore the cell of the sheriff from the stack.
49554 PUSH HL Stash the cell of the sheriff on the stack.
49555 INC L Add one to the column.
Draw the edges and the objects in the cell.
49556 CALL DrawCellAndObjects Call DrawCellAndObjects.
49559 POP HL Restore the cell of the sheriff from the stack.
49560 INC L Add one to the column...
49561 DEC H ...and take one off the row.
The last cell goes on into the routine, which returns to the caller.
DrawCellAndObjects 49562 PUSH HL Stash the cell on the stack.
Draw the edges of the cell.
49563 CALL DrawCell Call DrawCell.
49566 POP HL Restore the cell from the stack.
Continue on to DrawCellObjects.
View the equivalent code in;
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